As California's drought appears set to continue for a third year, the Department of the Interior has said that one of the state's most populated watersheds now faces major stress due to climate change and increased water demand.
The 2,650-square-mile Santa Ana River Watershed, which encompasses much of Southern California's Orange County, is likely to experience a decrease in surface water supply and a reduction in groundwater availability over the coming century, according to a study released last week by the Bureau of Reclamation.
At the same time, the U.S. Census Bureau projects that the region's population will grow from 6 million to nearly 10 million within the next half-century.
"In light of climate change, prolonged drought conditions, growth, and population projections, a strong concern exists to ensure there will be adequate water supplies to meet future demand," the study states.
The Santa Ana River Area watershed is the first urban area where Reclamation has completed a climate change analysis. It was created in collaboration with the Santa Ana Watershed Project Authority (SAWPA), which is integrating information from the report into its regional water management plan, set for formal adoption in February 2014.
"The bad news is, we're looking at radical changes that are going to challenge the way we think about water, manage water and use water," said Celeste Cantú, SAWPA's general manager. "The good news is, we have the capacity to respond -- but we have to change."
Stuck in the 'severe' drought category
The study comes at a time when California's water woes have been brought into focus due to drought that has so far dragged on for two years.
According to the most recent U.S. Drought Monitor, more than 97 percent of the state is still in drought, with more than 82 percent -- including the Santa Ana River Watershed -- stuck in the "severe" category. Two of the state's major reservoirs, Lake Oroville and Lake Shasta, were measured at under 40 percent full last week, the Associated Press reported.
Two California officials, Democratic Sen. Dianne Feinstein and Rep. Jim Costa, wrote a letter last Monday asking Gov. Jerry Brown (D) and President Obama to declare a drought emergency and federal disaster in the state (ClimateWire, Dec. 13).
Climate change is not going to make things any easier for the Santa Ana River Watershed. The Bureau of Reclamation projects that precipitation there will likely decrease over the long term. Meanwhile, the mercury is expected to go up, with the number of days seeing temperatures over 95 degrees Fahrenheit expected to quadruple by 2070 in Anaheim, Orange County's most populous city.
As a result of these and other factors, the study states, the region's annual surface water supply is projected to decline.
Groundwater, which today makes up more than 50 percent of the watershed's total supply, is also going to be under greater strain due to growth in demand and climate change. Because of precipitation decline and temperature decrease, aquifers will no longer be recharged to the extent they once were.
"Management actions such as reducing municipal and industrial water demands or increasing trans-basin water imports and recharge will be required in order to maintain current groundwater levels," the report states.
More storage, less lawn watering
But one of the biggest challenges for Santa Ana watershed's managers, said Cantú, is that future precipitation events will likely be highly erratic.
"We're going to probably have some years with almost no snow events, and some years with massive snow events," Cantú said. "We now have to engineer ... to capture that one massive event that might happen every three to five years. That means much more storage."
Additionally, these deluges will most often come in the form of rain rather than the winter snowpack the region has traditionally relied on for storage, doubling the likelihood of 200-year storm events and making the watershed much more vulnerable to flooding.
Dealing with this is going to be "a huge operational change," Cantú said.
The watershed authority is crafting plans to deal with these challenges with its upcoming "One Water One Watershed" water plan.
In addition to increasing storage potential, conserving water at the user level is one of the authority's biggest priorities.
"The biggest bang for our buck really is reducing demand and moving it into significant water use efficiency," said Mark Norton, water resources and planning manager for SAWPA.
In 2010, the state of California released its "20x2020 Water Conservation Plan," which SAWPA must comply with, requiring a 20 percent reduction in per-capita urban water use by 2020.
'Think about water differently'
Getting homeowners to reduce their outdoor water use -- that is, watering lawns -- is a major focus. For residents living in the inland portion of the Santa Ana Watershed, 80 percent of total water use goes toward sustaining lawns, according to Cantú.
"That's where our water savings are really going to be," she said.
Additionally, "with each water efficiency effort, there is energy savings, as well," Norton said. "We know that here in California, 19 percent of all energy use is associated with water pumping and distribution."
In addition to looming climate threats, the water authority is also compelled to reduce its energy use in light of California's A.B. 32 legislation, which requires the state's major sectors to reduce emissions to 1990 levels by 2020.
To address this, the new Reclamation study also addresses mitigation, creating a greenhouse gas calculator tool to help SAWPA reduce its emissions. "It's a great tool that other people across the state of California have shown real interest in," Norton said.
However, Cantú added, water authorities within the Santa Ana River Watershed Basin can't tackle climate change and the resulting water strain by themselves.
"This affects everybody who lives in our watershed, and everybody has a role to play," she said. "We can't do it alone, no matter how much money and smarts we have ... it requires every person who uses water to think about water differently."